Electromagnetic device



April 28, 1931. F. J. BULLIVANT ET AL ELECTROMAGNETI C DEVI CE FiledAug. 5, 1928 Z4 29 IN x g/v T0735 ATTORNEY Patented Apr- 28, 1931 uuran, STATES PATENT orrlca rumors 1. aunnxvm Anna-nan A. mum, or s'r.more, ,IIBSOUBI momemc navrcr:

, I Application flledAugunt 8, 1928. Serial No. 287,151. I

This invention relates generally to-electromagnetic devices and, moreparticularly, to a certain new and useful improvement in electromagneticdevices of a type especially.

' 6 adapted for use, as in radio, in the sending or receiving ofelectro-magnetic waves.

Our invention has for its prime object the provision in a device of thetype stated of an inductance unit characterized by being. electricallyand mechanicall protected and con-.

tained in an impermeab e moisture-free vessel, so as to have acalibrated electro-magnetic constant or constants.

Our invention has for another object the provision in a device of thetype stated of means for adjustably var ing the fundamental of thewindings an to, calibrate the same during the. process of manufacture toassure thatany one transformer will match any other having the sameintended induc tance value. Our invention has for a further object the'provision in a device of the type stated of shielding means disposed onthe walls of the vessel and associated with its contained windings infixed relation thereto, whereby the electro-ma-gnetic constants of thedevice. may be ermanently calibrated.

ur invention has for a still further object the provision in a device ofthe type stated of means whereby the inductance unitmay be easily andquickly incorporated in its associated circut or circuits, as by lugginthe unit in, for example, a stan ard tu e socket or like receptacle.

And with the above and other objects in view, our invention resides inthe novel fea-- tures of form, construction, arran ement, andcombination of parts hereina er described and pointed out in the claims.

In the accompanying drawing, the figure illustrates'one form of anelectromagnetic device embodying our invention, parts thereof beingshown in section and other parts being broken away to disclose theconstruction of the device.

Referring now more in detail and by reference characters'to the drawing,which illustrates a preferred embodiment of our invention, our improvedmductance unit may 1nclude a transformer A comprising an associated oupof inductances or electro-magnetic windings sealed in an impermeablevessel or chamber C preferably made of a dielectric, such as glass,having a moisture free content, as by being evacuated or filled with adry, inert gas, and for convenience in handling and mounting the unit wemay afiix a base D to-the bulb C, said base preferably carrying contactmembers connected to the transformer .A and adaptedto mate with astandard tube socket (not shown).

The transformer A may include a secondary inductance 10 wound on aninsulatin form 11, and a primary inductance 12 wound on an insulatingform 13 inserted within and preferably complementary to the form 11,with the outer or battery terminal B of the winding 12 adjacent one orthe grid terminal G of the windmg 10, thus disposing the high potentialterminals of the irespectlve inductubes in efiicient relationship formaximum magnetic coupling consistent with minimum capacity leakagebetween the windings.

The forms 11 and 13 may beof circular octagonal, square or othercross-section, an may be of tubular or skeleton construction, but weprefer to employ, as shown, circular tubular forms.

It isobvious that one, two, or more windperson constructing the device.The inductances maybe wound for use in radio-frequency or audiofrequencycircuits, and 0th er dispositions and arrangements of the severalwindings, in addition to that shown on the drawings, will be obvious tothose skilled in the art.

The moisture free vessel or chamber C includes a glass or likeimpermeable dielectri'c bulb 14 preferably formed at one or the basewall 15 thereof with an inwardly presented inte al transformer support16, pref erably having a chamber 17 opening at its outer end throughsaid base wall 15,

The vessel C may have an egg-shape, as shown in the drawing, or it mayhave the shape of a spheriod, an ovaloid, or other coo formation, andpreferably is made moisturegas, as nitrogen, and immersing theinductance in said gas.

Having one end supportingly .passed through pairs of alining ferrules18a, 18b,

disposed oppositely in and suitably cri-mped or otherwise secured to therespective forms 11- and 13, and the other end embedded in a cap 19forming the inner end of the inductance support 16 and the endwall ofthechamber 17, are opposing inductance supporting members or arms 20,suitably bent as best seen in the drawing, and fixed in the ferrules byany suitable means, although we prefer to employ solder, as at 21,whereby the transformer A is firmly endwise supported as a unit in thevessel C.

By thus supporting and sealing the transformer A in the closed vessel orchamber C,

the windings 10, 12, are protected from atmospheric influences, such ashygroscopic moisture, and particularly variations in the humidity of theatmosphere, the contents of said vessel or chamber being alsomoisturefree, thereby effectually preventing, from any cause, theformation of aqueous films on the windings, as well as at the same timepreventing the deposition on the windings of films of dust or fume orthe like. Such several films have the deleterious effect of increasingthe inter-turn capacity leaka' of the windings, and of also increasingthe ighfrequency resistance loss of the transformer, and as they varyfrom time to time, their growth and decay seriously deranges theconstancy of the inductance value of windings exposed to theirinfluence.

Furthermore, the windings being thus permanently and rigidly disposed inthe containing vessel C, the latter forms a protecting envelope toprevent mechanical derangement or damage from handling or like causes.

The base D includes a molded cup or like structure 22 of insulatingmaterial, aving a filling of suitable insulating adhesive compound 23,in which is seated and secured the wall 15 of the bulb C, said wall 15preferably having a frusto-conical shape as shown, presented interiorlysaid cup 22. Endwise presented from one or the bottom wall 24 of the cup22 for mating with a suitable socket (not shown), such as a standardtube socket well known to those skilled in the art, are contact prongsF, P, B and G, adapted, respectively to be connected with appropriatefilament, late, battery and grid or other leads, of t e circuit withwhich the inductance is associated.

The filament terminal F and the grid terminal G of the secondary windingare, re spectively, secured to the form 11 preferably by being passedthrough suitable apertures 25 there1n,-and are connected to the res c21. Embedded in the cap 19 and filling 23 and passed through suitableinsulating tubes 26 dlsposedin the chamber17, are conducttive ferrules18a, preferably by the so der A ing leads 27, 28, respectivelyconnecting the terminals F and G to the corresponding terminal lugs 29of the rongs F and G embedded in and exten ing through the wall 24 ofthe base D. 5 I In like manner, the plate terminal P an the batteryterminal B of the rimary winding 12 are, respectively, passed throughsuitable apertures 30 provided in the form 13 and are connected toconnection In s 31 secured to the form 13. Conducti eads 32, 33, formedand disposed similar y to the leads 27,28, connect the terminals P and Bthrough their respective lugs 31 to the terminal lugs 29 of theircorresponding prongs P and B.

Preferably mounted on the form 11 adjacent to the filament end of thewinding 10 and connected to the terminal F by a conducting lead 34passed through an aperture 35 in said form 11, is a metallic capacityelement or absorption plate 36, which acts to reduce the fundamental of"the secondary winding. In manufacturing the device, the late 36 may beadjusted suitably to alter the inductance value of the unit to match apredetermined standard value, so that any several transformers eachhaving an associated group of inductances will have the same calibratedvalue in, for example, milli-henries, a condition referred to in the artas matched inductances. Exteriorly applied in a continuous conductingfilm, by electro-depositing, painting, spraying or dipping, to theexposed surface of the vessel C and baseD, is a metallic paint or likematerial 37, said paint being omitted from the wall 24, however, inorder not to short-circuit the several prongs presented therefrom. Aband 38 encircles the base D, contacting said conducting film 37, and ispreferably connected to the filament prong F by a lead or conductor 39,said prong F being commonly associated with the negative or groundedside of the circuit in which the.

transformer is intended to be incor orated.

-. We prefer to form thefilm 37 o alumi.

num' paint forming an electro-magnetic absorption medium, whereby thetransformer A is effectually shielded from exterior magthereto-adjacent, and theshield being fixed with respect to thewindings, the magnetic field of the transformer has a constant extentand value. I

In the u'seof our invention, the several windings maybe employed in, orassociated with, any desired circuit in the usual manner well known tothe art, the base D, having the several contact prongs, providing aconvenient and practical means of connecting the windings to theirappropriate parts of the circuit by simply plugging the device into asuitable socket or receptacle provided in the apparatus incorporatingthe circuit.

Thus it will be seen that we have provided a simple, neat, andconvenient inductance unit or transformer, the windings of which aredisposed in permanent and fixed relation in a moisture-free impermeablechamber or vessel, whereby the inter-turn capacity leakage of thewindings is minimized, the windings are protected from corrosion or likedeleterious influence of moisture, from the deposition of dust or fumeor the like, and from mechanical derangement or damage in handling,hence the calibration of the transformer or inductance unit, once ef--fected, remains thereafter at a constant value, an important and vitalfeature in radio-receiving or sending apparatus;

It is to be understood that changes in the form, construction,arrangement, and combination of the several parts of our new device .maybe made and substituted for those herein shown and described withoutdeparting from the nature and principle of our iiivention.

Having thus described our invention, what we claim and desire to secureby Letters Pat ent is:

1. In combination, a base of insulating material, a sealedevacuated-glass bulb having a conical endwall presented into and securedto said base, an interiorly presented supporting member integrallyextending from said endwall, a pair of spaced arms having one endembedded in said support, a pair of electro-magnetically associatedinductance windings rigidly supported on the other ends of said arms, aplurality of contact prongs exteriorly presented from the end wall ofsaid base, conducting members connected to said contact prongs andsealed through said supporting member for establishing electricalconnection between said prongs and the respective terminals of saidwindings, a coat ing of conducting material applied to the exposed wallsof, said base and said bulb, said prongs being insulated from saidooatin a. conducting band encircling said base for e ectrical contactwith said coating, and means for electrically connecting said band withone of said prongs. r

2. In combination, a base of insulating material, a sealed evacuatedglassbulb having an end Wall presented into and secured to said base, aninteriorl presented supporting member extending rom said end wall, apair of spaced arms having one end fixed to said support, a plurality ofelectro-magnetically associated inductance windings rigidly supbulb,said prongs being) ported on the other ends of said arms, a plurality ofcontact prongs exteriorly presented from the end wall of said base,conducting members connected to said contact prongs and sealed throughsaid supporting member for establishing electrical connection betweensaid prongs and the respective terminals of said windings, a coating ofconducting material applied to the walls of said base and said insulatedfrom said coating, a conductin and on the base for electrical contactwith said coating, and means for electrically connecting said bandwith'one of said prongs.

In testimony whereof, we have signed our names to this specification.

FRANCIS J. BULLIVAN'I.

FRED A. MILLER.

